Assess the clutter.
Start by creating three categories: keep, donate, and toss. As you go through the items, assign each one to a category. If you rarely use a piece, it’s probably a good candidate for the donate or toss pile.
Donate or toss.
Contact local charities and arrange for a pickup of items to be donated; put the toss items out with the trash or recycling.
Edit the keep pile.
Sort the items you’re keeping into new categories, such as sporting equipment, power tools, etc. Assign each category a location: Sporting equipment, for example, might go in a wall cabinet or a bin in a corner; power tools might be hung on a system of hooks on a large piece of Peg-Board.
Give anything that is not plainly identifiable a clear label. (Tuck a permanent marker and blue painter’s tape in a zippered plastic sandwich bag and have the kit handy for labeling anything and everything.)
Choose the right shelving.
Consider installing metal shelving. It’s affordable, easy to assemble, and able to withstand heat and humidity better than wood. Shelves will also keep your valuables safe from any dampness on the floor.
Pick plastic storage boxes.
Cardboard boxes, no matter how strong, bend and dent with frequent use and eventually succumb to dampness. Waterproof plastic containers protect their contents better, seal tighter, and are easy to carry or shift around on shelves (as long as they aren’t too big).
Hang items to save space.
Think about putting up pegs or hooks for such items as bicycles, cords, hoses, tools, strollers, and shovels. String up a hammock in the corner of the garage to hold roly-poly gear, like basketballs.